Self-activating chitosan-based nanoparticles for sphingosin-1 phosphate modulator delivery and selective tumor therapy.

This study reports on the design and synthesis of hypoxia responsive nanoparticles (HRNPs) composed of methoxy polyethylene glycol-4,4 dicarboxylic azolinker-chitosan (mPEG-Azo-chitosan) as ideal drug delivery platform for Fingolimod (FTY720, F) delivery to achieve selective and highly enhanced TNBC therapy in vivo. Herein, HRNPs with an average size of 49.86 nm and a zeta potential of +3.22 mV were synthetized, which after PEG shedding can shift into a more positively-charged NPs (+30.3 mV), possessing self-activation ability under hypoxia situation in vitro, 2D and 3D culture. Treatment with lower doses of HRNPs@F significantly reduced MDA-MB-231 microtumor size to 15 %, induced apoptosis by 88 % within 72 h and reduced highly-proliferative 4 T1 tumor weight by 87.66 % vs. ∼30 % for Fingolimod compared to the untreated controls. To the best of our knowledge, this is the first record for development of hypoxia-responsive chitosan-based NPs with desirable physicochemical properties, and selective self-activation potential to generate highly-charged nanosized tumor-penetrating chitosan NPs. This formulation is capable of localized delivery of Fingolimod to the tumor core, minimizing its side effects while boosting its anti-tumor potential for eradication of TNBC solid tumors.

Identification of FTY720 and COH29 as novel topoisomerase I catalytic inhibitors by experimental and computational studies.

The development of novel topoisomerase I (TOP1) inhibitors is crucial for overcoming the drawbacks and limitations of current TOP1 poisons. Here, we identified two potential TOP1 inhibitors, namely, FTY720 (a sphingosine 1-phosphate antagonist) and COH29 (a ribonucleotide reductase inhibitor), through experimental screening of known active compounds. Biological experiments verified that FTY720 and COH29 were nonintercalative TOP1 catalytic inhibitors that did not induce the formation of DNA-TOP1 covalent complexes. Molecular docking revealed that FTY720 and COH29 interacted favorably with TOP1. Molecular dynamics simulations revealed that FTY720 and COH29 could affect the catalytic domain of TOP1, thus resulting in altered DNA-binding cavity size. The alanine scanning and interaction entropy identified Arg536 as a hotspot residue. In addition, the bioinformatics analysis predicted that FTY720 and COH29 could be effective in treating malignant breast tumors. Biological experiments verified their antitumor activities using MCF-7 breast cancer cells. Their combinatory effects with TOP1 poisons were also investigated. Further, FTY720 and COH29 were found to cause less DNA damage compared with TOP1 poisons. The findings provide reliable lead compounds for the development of novel TOP1 catalytic inhibitors and offer new insights into the potential clinical applications of FTY720 and COH29 in targeting TOP1.

Neutrophil Membrane-Camouflaged Polyprodrug Nanomedicine for Inflammation Suppression in Ischemic Stroke Therapy.

Neuroinflammation has emerged as a major concern in ischemic stroke therapy because it exacebates neurological dysfunction and suppresses neurological recovery after ischemia/reperfusion. Fingolimod hydrochloride (FTY720) is an FDA-approved anti-inflammatory drug which exhibits potential neuroprotective effects in ischemic brain parenchyma. However, delivering a sufficient amount of FTY720 through the blood-brain barrier into brain lesions without inducing severe cardiovascular side effects remains challenging. Here, a neutrophil membrane-camouflaged polyprodrug nanomedicine that can migrate into ischemic brain tissues and in situ release FTY720 in response to elevated levels of reactive oxygen species. This nanomedicine delivers 15.2-fold more FTY720 into the ischemic brain and significantly reduces the risk of cardiotoxicity and infection compared with intravenously administered free drug. In addition, single-cell RNA-sequencing analysis identifies that the nanomedicine attenuates poststroke inflammation by reprogramming microglia toward anti-inflammatory phenotypes, which is realized via modulating Cebpb-regulated activation of NLRP3 inflammasomes and secretion of CXCL2 chemokine. This study offers new insights into the design and fabrication of polyprodrug nanomedicines for effective suppression of inflammation in ischemic stroke therapy.

Pharmacological Effects of FTY720 and its Derivatives.

FTY720 is an analog of sphingosine-1-phosphate (S1P) derived from the ascomycete Cordyceps sinensis. As a new immunosuppressant, FTY720 is widely used to treat multiple sclerosis. FTY720 binds to the S1P receptor after phosphorylation, thereby exerting immunosuppressive effects. The nonphosphorylated form of FTY720 can induce cell apoptosis, enhance chemotherapy sensitivity, and inhibit tumor metastasis of multiple tumors by inhibiting SPHK1 (sphingosine kinase 1) and activating PP2A (protein phosphatase 2A) and various cell death pathways. FTY720 can induce neutrophil extracellular traps to neutralize and kill pathogens in vitro, thus exerting anti- infective effects. At present, a series of FTY720 derivatives, which have pharmacological effects such as anti-tumor and alleviating airway hyperresponsiveness, have been developed through structural modification. This article reviews the pharmacological effects of FTY720 and its derivatives.

Potential role of marine species-derived bioactive agents in the management of SARS-CoV-2 infection.

COVID-19, caused by the SARS-CoV-2 outbreak, has resulted in a massive global health crisis. Bioactive molecules extracted or synthesized using starting material obtained from marine species, including griffithsin, plitidepsin and fingolimod are in clinical trials to evaluate their anti-SARS-CoV-2 and anti-HIV efficacies. The current review highlights the anti-SARS-CoV-2 potential of marine-derived phytochemicals explored using in silico, in vitro and in vivo models. The current literature suggests that these molecules have the potential to bind with various key drug targets of SARS-CoV-2. In addition, many of these agents have anti-inflammatory and immunomodulatory potentials and thus could play a role in the attenuation of COVID-19 complications. Overall, these agents may play a role in the management of COVID-19, but further preclinical and clinical studies are still required to establish their role in the mitigation of the current viral pandemic.

Macrophage-Disguised Manganese Dioxide Nanoparticles for Neuroprotection by Reducing Oxidative Stress and Modulating Inflammatory Microenvironment in Acute Ischemic Stroke.

Reperfusion injury is still a major challenge that impedes neuronal survival in ischemic stroke. However, the current clinical treatments are remained on single pathological process, which are due to lack of comprehensive neuroprotective effects. Herein, a macrophage-disguised honeycomb manganese dioxide (MnO2 ) nanosphere loaded with fingolimod (FTY) is developed to salvage the ischemic penumbra. In particular, the biomimetic nanoparticles can accumulate actively in the damaged brain via macrophage-membrane protein-mediated recognition with cell adhesion molecules that are overexpressed on the damaged vascular endothelium. MnO2 nanosphere can consume excess hydrogen peroxide (H2 O2 ) and convert it into desiderated oxygen (O2 ), and can be decomposed in acidic lysosome for cargo release, so as to reduce oxidative stress and promote the transition of M1 microglia to M2 type, eventually reversing the proinflammatory microenvironment and reinforcing the survival of damaged neuron. This biomimetic nanomedicine raises new strategy for multitargeted combined treatment of ischemic stroke.

Selenium nanoparticles coated with pH responsive silk fibroin complex for fingolimod release and enhanced targeting in thyroid cancer.

Cancer-targeted drug delivery systems based on nanoparticles (NPs) have been considered promising therapies. In this study, we developed a pH-responsive smart NPs drug delivery system using silk fibroin (SF), selenium nanoparticles (Se NPs), fingolimod (FTY720), and heptapeptide (T7). The prepared FTY720@T7-SF-Se NPs were spheres with an average diameter of 120 nm, which would contribute to the enhanced permeability and retention effects in tumour regions. The encapsulation efficiency (EE) of the FTY720@T7-SF-Se NPs was 71.95 ± 3.81%. The release of FTY720 from the nanocarriers was pH-dependent, and the release of FTY720 was accelerated in an acidic environment. Both in vitro and in vivo studies showed that FTY720@T7-SF-Se NPs had an enhanced cellular uptake selectivity and antitumor activity for thyroid cancer. The bio-distribution study in vivo further demonstrated that FTY720@T7-SF-Se NPs could effectively accumulate in the tumour region, thereby enhancing the ability to kill cancer cells in vivo. In addition, studies of histology and immunohistochemistry showed that FTY720@T7-SF-Se NPs had low toxicity to the major organs of tumour-bearing mice, indicating the prepared NPs has good biocompatibility in vivo. These results suggest that the tumour-targeted NPs delivery system (FTY720@T7-SF-Se NPs) has great potential as a new tool for thyroid cancer therapy.

In vitro anticancer evaluation of micelles containing N-(4-(2-((4-methoxybenzyl)amino)ethyl)phenyl)heptanamide, an analogue of fingolimod.

Fingolimod has been evaluated for use as an anticancer agent. However, many steps are required to synthesize fingolimod because of its intricate structure. A fingolimod analogue, N-(4-(2-((4-methoxybenzyl)amino)ethyl)phenyl)heptanamide (MPH), also has anti-cancer effects and is easier to synthesize but is poorly soluble in water. To compensate for its poor water solubility, MPH-loaded polymeric micelles were prepared by thin film hydration method using various polymers and the physicochemical properties of the MPH-loaded micelles such as particle size, drug-loading (DL, %), and encapsulation efficiency (EE, %) were evaluated. A storage stability test was conducted to select the final formulation and the release profile of the MPH-loaded micelles was confirmed by in vitro release assay. MPH-loaded mPEG-b-PLA micelles were selected for further testing based on their stability and physicochemical properties; they were stable for stable for 14 days at 4 °C and 25 °C and for 7 days at 37 °C. They showed anti-cancer efficacy against both A549 and U87 cancer cells. Encapsulation of MPH in polymeric micelles did not decrease the in vitro cytotoxicity of MPH. The findings of this study lay the groundwork for future formulations that enable the effective and stable delivery of poorly water-soluble agents.

Local delivery of FTY720 in mesoporous bioactive glass improves bone regeneration by synergistically immunomodulating osteogenesis and osteoclastogenesis.

The addition of osteoimmunology drugs to bone repair materials is beneficial to bone regeneration by regulating the local immune microenvironment. Fingolimod (FTY720) has been reported to be an osteoimmunology drug that promotes osteogenesis. However, there is no ideal biomaterial for the sustained release of FTY720 in the bone defect areas. In the present work, FTY720 loaded mesoporous bioactive glass (FTY720@MBGs) was successfully prepared based on the mesoporous properties of MBGs and electrostatic attraction. FTY720 achieved a sustained release for 7 days. The in vitro study found that FTY720@MBGs could synergistically promote osteogenesis and inhibit osteoclastogenesis due to their ability to promote macrophages toward the M2 phenotype. The in vivo study confirmed that FTY720@MBGs could significantly improve bone regeneration. This study provides new strategies for designing smart cell-instructive biomaterials that can play a role in all bone healing processes from early inflammation to bone reconstruction.

Biocompatible Chemotherapy for Leukemia by Acid-Cleavable, PEGylated FTY720.

Targeting the inability of cancerous cells to adapt to metabolic stress is a promising alternative to conventional cancer chemotherapy. FTY720 (Gilenya), an FDA-approved drug for the treatment of multiple sclerosis, has recently been shown to inhibit cancer progression through the down-regulation of essential nutrient transport proteins, selectively starving cancer cells to death. However, the clinical use of FTY720 for cancer therapy is prohibited because of its capability of inducing immunosuppression (lymphopenia) and bradycardia when phosphorylated upon administration. A prodrug to specifically prevent phosphorylation during circulation, hence avoiding bradycardia and lymphopenia, was synthesized by capping its hydroxyl groups with polyethylene glycol (PEG) via an acid-cleavable ketal linkage. Improved aqueous solubility was also accomplished by PEGylation. The prodrug reduces to fully potent FTY720 upon cellular uptake and induces metabolic stress in cancer cells. Enhanced release of FTY720 at a mildly acidic endosomal pH and the ability to substantially down-regulate cell-surface nutrient transporter proteins in leukemia cells only by an acid-cleaved drug were confirmed. Importantly, the prodrug demonstrated nearly identical efficacy to FTY720 in an animal model of BCR-Abl-driven leukemia without inducing bradycardia or lymphopenia in vivo, highlighting its potential clinical value. The prodrug formulation of FTY720 demonstrates the utility of precisely engineering a drug to avoid undesirable effects by tackling specific molecular mechanisms as well as a financially favorable alternative to new drug development. A multitude of existing cancer therapeutics may be explored for prodrug formulation to avoid specific side effects and preserve or enhance therapeutic efficacy.

Improving hard palate wound healing using immune modulatory autotherapies.

Oral cavity wound healing occurs in an environment that sustains ongoing physical trauma and is rich in bacteria. Despite this, injuries to the mucosal surface often heal faster than cutaneous wounds and leave less noticeable scars. Patients undergoing cleft palate repair have a high degree of wound healing complications with up to 60% experiencing oronasal fistula (ONF) formation. In this study, we developed a mouse model of hard palate mucosal injury, to study the endogenous injury response during oral cavity wound healing and ONF formation. Immunophenotyping of the inflammatory infiltrate following hard palate injury showed delayed recruitment of non-classical LY6Clo monocytes and failure to resolve inflammation. To induce a pro-regenerative inflammatory response, delivery of FTY720 nanofiber scaffolds following hard palate mucosal injury promoted complete ONF healing and was associated with increased LY6Clo monocytes and pro-regenerative M2 macrophages. Alteration in gene expression with FTY720 delivery included increased Sox2 expression, reduction in pro-inflammatory IL-1, IL-4 and IL-6 and increased pro-regenerative IL-10 expression. Increased keratinocyte proliferation during ONF healing was observed at day 5 following FTY720 delivery. Our results show that local delivery of FTY720 from nanofiber scaffolds in the oral cavity enhances healing of ONF, occurring through multiple immunomodulatory mechanisms. STATEMENT OF SIGNIFICANCE: Wound healing complications occur in up to 60% of patients undergoing cleft palate repair where an oronasal fistula (ONF) develops, allowing food and air to escape from the nose. Using a mouse model of palate mucosal injury, we explored the role of immune cell infiltration during ONF formation. Delivery of FTY720, an immunomodulatory drug, using a nanofiber scaffold into the ONF was able to attract anti-inflammatory immune cells following injury that enhanced the reepithelization process. ONF healing at day 5 following FTY720 delivery was associated with altered inflammatory and epithelial transcriptional gene expression, increased anti-inflammatory immune cell infiltration, and increased proliferation. These findings demonstrate the potential efficacy of immunoregenerative therapies to improve oral cavity wound healing.

In search of constrained FTY720 and phytosphingosine analogs as dual acting anticancer agents targeting metabolic and epigenetic pathways.

A series of compounds containing pyrrolidine and pyrrolizidine cores with appended hydrophobic substituents were prepared as constrained analogs of FTY720 and phytosphingosine. The effect of these compounds on the viability of cancer cells, on downregulation of the nutrient transport systems, and on their ability to cause vacuolation was studied. An attempt to inhibit HDACs with some phosphate esters of our analogs was thwarted by our failure to reproduce the reported inhibitory action of FTY720-phosphate.

Synthesis and Biological Evaluation of FTY720 (Fingolimod) Derivatives with Aromatic Head Group as Anticancer Agents.

FTY720 is employed for the treatment of multiple sclerosis and exerts apoptotic effects on various cancers through protein phosphatase 2A (PP2A) activation. In compound 4, the dihydroxy head group of FTY720 was modified into dihydroxy phenyl group. The cell survival in compound 4 treated colorectal and gastric cancer cells was significantly reduced as compared with control, 34.6 and 25.1%, respectively. The docking study of compound 4 showed that the aromatic head group effectively binds to PP2A.

S1PR3 is essential for phosphorylated fingolimod to protect astrocytes against oxygen-glucose deprivation-induced neuroinflammation via inhibiting TLR2/4-NFκB signalling.

Fingolimod (FTY720) is used as an immunosuppressant for multiple sclerosis. Numerous studies indicated its neuroprotective effects in stroke. However, the mechanism remains to be elucidated. This study was intended to investigate the mechanisms of phosphorylated FTY720 (pFTY720), which was the principle active molecule in regulating astrocyte-mediated inflammatory responses induced by oxygen-glucose deprivation (OGD). Results demonstrated that pFTY720 could protect astrocytes against OGD-induced injury and inflammatory responses. It significantly decreased pro-inflammatory cytokines, including high mobility group box 1 (HMGB1) and tumour necrosis factor-α (TNF-α). Further, studies displayed that pFTY720 could prevent up-regulation of Toll-like receptor 2 (TLR2), phosphorylation of phosphoinositide 3-kinase (PI3K) and nuclear translocation of nuclear factor kappa B (NFκB) p65 subunit caused by OGD. Sphingosine-1-phosphate receptor 3 (S1PR3) knockdown could reverse the above change. Moreover, administration of TLR2/4 blocker abolished the protective effects of pFTY720. Taken together, this study reveals that pFTY720 depends on S1PR3 to protect astrocytes against OGD-induced neuroinflammation, due to inhibiting TLR2/4-PI3K-NFκB signalling pathway.

Benefit-Risk Profile of Sphingosine-1-Phosphate Receptor Modulators in Relapsing and Secondary Progressive Multiple Sclerosis.

Since the approval of fingolimod, several selective sphingosine-1-phosphate receptor modulators have entered clinical development for multiple sclerosis. However, side effects can occur with sphingosine-1-phosphate receptor modulators. By considering short-term data across the drug class and longer term fingolimod data, we aim to highlight the potential of sphingosine-1-phosphate receptor modulators in multiple sclerosis, while offering reassurance that their benefit-risk profiles are suitable for long-term therapy. Short-term fingolimod studies demonstrated the efficacy of this drug class, showed that cardiac events upon first-dose administration are transient and manageable, and showed that serious adverse events are rare. Early-phase studies of selective sphingosine-1-phosphate receptor modulators also show efficacy with a similar or improved safety profile, and treatment initiation effects were reduced with dose titration. Longer term fingolimod studies demonstrated sustained efficacy and raised no new safety concerns, with no increases in macular edema, infection, or malignancy rates. Switch studies identified no safety concerns and greater patient satisfaction and persistence with fingolimod when switching from injectable therapies with no washout period. Better outcomes were seen with short than with long washouts when switching from natalizumab. The specific immunomodulatory effects of sphingosine-1-phosphate receptor modulators are consistent with the low observed rates of long-term, drug-related adverse effects with fingolimod. Short-term data for selective sphingosine-1-phosphate receptor modulators support their potential effectiveness in multiple sclerosis, and improved side-effect profiles may widen patient access to this drug class. The long-term safety, tolerability, and persistence profiles of fingolimod should reassure clinicians that sphingosine-1-phosphate receptor modulators are likely to be suitable for the long-term treatment of multiple sclerosis.

Pharmacological Activation of Protein Phosphatase 2 A (PP2A): A Novel Strategy to Fight Against Human Malignancies?

BACKGROUND: The serine-threonine protein phosphatase 2A (PP2A) regulates multiple cell signaling cascades and its inactivation by viral oncoproteins, mutation of specific structural subunits or upregulation of the cellular endogenous inhibitors may contribute to malignant transformation by regulating specific phosphorylation events. Pharmacological modulation of PP2A activity is becoming an attractive strategy for cancer treatment. Some compounds targeting PP2A are able to induce PP2A reactivation and subsequent cell death in several types of cancer. METHODS: We undertook a search of bibliographic databases for peer-reviewed articles focusing on the main item of the review. We selected articles published in indexed journals. The quality of retrieved papers was appraised using the standard bibliometric indicators. RESULTS: One hundred and fourteen papers were included in the review. Twenty-seven papers gave an overview of structure and physiological role of PP2A. Twenty-five papers outlined the role of PP2A in tumor suppression. Forty papers analyzed the mechanism involved in PP2A reactivation by synthetic compounds, and twenty-two papers outlined the capability of natural compounds of restoring PP2A activity and how this could be beneficial. CONCLUSION: Findings analyzed in this review underline the central role of PP2A as a regulator of cell growth and survival, hence its function as tumor suppressor. The discovery that some compounds, either synthetic or natural, are capable of reactivating PP2A opens up new perspectives for future strategies to fully exploit therapeutic potential in human cancer. Thus, this review could also be of particular interest to pharmaceutical or biotechnology companies for drug design and targeted delivery.

Development of novel PP2A activators for use in the treatment of acute myeloid leukaemia.

AAL(S), the chiral deoxy analog of the FDA approved drug FTY720, has been shown to inhibit proliferation and apoptosis in several cancer cell lines. It has been suggested that it does this by activating protein phosphatase 2A (PP2A). Here we report the synthesis of new cytotoxic analogs of AAL(S) and the evaluation of their cytotoxicity in two myeloid cell lines, one of which is sensitive to PP2A activation. We show that these analogs activate PP2A in these cells supporting the suggested mechanism for their cytotoxic properties. Our findings identify key structural motifs required for anti-cancer effects.

Therapeutic Potential of the Modulation of Sphingosine-1-Phosphate Receptors.

It is accepted that sphingolipids (SL) are not only structural lipids in cellular membranes, but also key regulators of different cell process. Sphingosine-1-phosphate (S1P) is a member of this family involved, inter alia, in cell migration, angiogenesis and cell proliferation processes, being able to play different intracellular and extracellular roles. When S1P is transported out of the cell, it binds S1P specific G protein-coupled receptors, which are mainly involved in the regulation of the immune, vascular and nervous systems. These effects account for the vast diversity of functions that arise from the activation of S1P receptors. Deregulation of S1P levels is correlated with several pathologies, such as autoimmune disorders and cancer. Consequently, the correct modulation of these receptors represents a valuable approach for the development of new therapeutic strategies. Along this line, the non-selective S1P receptor agonist fingolimod (FTY720) has been commercialized recently for the treatment of multiple sclerosis and several related S1P receptor modulators are ongoing clinical trials. However, despite the progress in this field, the biological functions of S1P receptors are not still well elucidated. For this reason, several studies are being developed in order to better understand the functions of these receptors, making use of new selective S1P receptor agonists and antagonists as pharmacological tools.

Sphingosine kinase 1 is a reliable prognostic factor and a novel therapeutic target for uterine cervical cancer.

Sphingosine kinase 1 (SPHK1), an oncogenic kinase, has previously been found to be upregulated in various types of human malignancy and to play a crucial role in tumor development and progression. Although SPHK1 has gained increasing prominence as an important enzyme in cancer biology, its potential as a predictive biomarker and a therapeutic target in cervical cancer remains unknown. SPHK1 expression was examined in 287 formalin-fixed, paraffin-embedded cervical cancer tissues using immunohistochemistry, and its clinical implications and prognostic significance were analyzed. Cervical cancer cell lines including HeLa and SiHa were treated with the SPHK inhibitors SKI-II or FTY720, and effects on cell survival, apoptosis, angiogenesis, and invasion were examined. Moreover, the effects of FTY720 on tumor growth were evaluated using a patient-derived xenograft (PDX) model of cervical cancer. Immunohistochemical analysis revealed that expression of SPHK1 was significantly increased in cervical cancer compared with normal tissues. SPHK1 expression was significantly associated with tumor size, invasion depth, FIGO stage, lymph node metastasis, and lymphovascular invasion. Patients with high SPHK1 expression had lower overall survival and recurrence-free survival rates than those with low expression. Treatment with SPHK inhibitors significantly reduced viability and increased apoptosis in cervical cancer cells. Furthermore, FTY720 significantly decreased in vivo tumor weight in the PDX model of cervical cancer. We provide the first convincing evidence that SPHK1 is involved in tumor development and progression of cervical cancer. Our data suggest that SPHK1 might be a potential prognostic marker and therapeutic target for the treatment of cervical cancer.

Sphingosine 1 Phosphate at the Blood Brain Barrier: Can the Modulation of S1P Receptor 1 Influence the Response of Endothelial Cells and Astrocytes to Inflammatory Stimuli?

The ability of the Blood Brain Barrier (BBB) to maintain proper barrier functions, keeping an optimal environment for central nervous system (CNS) activity and regulating leukocytes' access, can be affected in CNS diseases. Endothelial cells and astrocytes are the principal BBB cellular constituents and their interaction is essential to maintain its function. Both endothelial cells and astrocytes express the receptors for the bioactive sphingolipid S1P. Fingolimod, an immune modulatory drug whose structure is similar to S1P, has been approved for treatment in multiple sclerosis (MS): fingolimod reduces the rate of MS relapses by preventing leukocyte egress from the lymph nodes. Here, we examined the ability of S1P and fingolimod to act on the BBB, using an in vitro co-culture model that allowed us to investigate the effects of S1P on endothelial cells, astrocytes, and interactions between the two. Acting selectively on endothelial cells, S1P receptor signaling reduced cell death induced by inflammatory cytokines. When acting on astrocytes, fingolimod treatment induced the release of a factor, granulocyte macrophage colony-stimulating factor (GM-CSF) that reduced the effects of cytokines on endothelium. In an in vitro BBB model incorporating shear stress, S1P receptor modulation reduced leukocyte migration across the endothelial barrier, indicating a novel mechanism that might contribute to fingolimod efficacy in MS treatment.